1. Field of the Invention
The present invention relates in general to digital subscriber line (DSL) communications, and in particular to DSL customer premises equipment (CPE) modems (DCPEs). The invention also relates to other types of communication devices, including cellular phones and other portable communication devices.
2. Background of the Invention
Upon startup of a DSL customer premises equipment (CPE) modem (DCPE), an application image is loaded and executed by the DCPE and is then used to control the operation of the DCPE. In existing DCPEs, the application image is stored in an onboard flash memory. Disadvantageously, the onboard flash memory used to store the application image is expensive, contributing to and increasing the overall cost of the DCPE. It would thus be beneficial to eliminate the need for these onboard flash memories, or their equivalent, in the manufacture of DCPEs.
DSL modems have used protocols such as BOOTP (as defined in IETF RFC-951) and TFTP (as defined in IETF RFC-783) to download the application image from the central office (CO), but only in the context of upgrading an existing application image that resides in the modem's onboard flash memory. These modems did not eliminate the requirement of having an onboard flash memory, since the modems still needed the application image to start up, initialize, and set up a data link with the CO before the new application image upgrade could be downloaded. Hence, these modems still required a flash memory, or its equivalent, and thus suffered from the drawbacks associated therewith.
Moreover, existing DCPEs are limited in their ability to add features or fix software defects by upgrading their software code. For example, adding features and/or fixing defects in the application image may result in increased application image size. The larger application image may not fit into the original onboard flash that was included when the DCPE was shipped to the customer. Therefore, storing the application image in an onboard flash memory also limits the ability to upgrade the application image itself.
Besides the additional cost and limitation on the application image size, storing the application image for the modems in an onboard flash memory makes it more difficult to push upgrades to the application from the CO. Because DCPEs often include an integrated NAT-firewall-router, the network architecture of the CPE is hidden from the services provider. This may allow the customers to deploy more LAN devices and computers than what is allowed under the customer's plan (e.g., the number of devices paid for under the agreement with the services provider). Accordingly, storing the application image in an onboard flash memory can make it more difficult to push upgrades to the application image and configuration as well as enforce data services plans.
Accordingly, it would be desirable to have a DCPE that could operate without an application image stored in an onboard flash memory, thus reducing the manufacturing cost of the modem and avoiding the inherent disadvantages involved with storing the application image onboard the DCPE.